In a communications network, network elements such as switches and routers route data from traffic flows to their destinations. Inside a network element, traffic is segmented into fixed-length cells. Traffic flows are comprised of packets, with each packet comprising one or more cells after this “segmentation” stage. Each cell is processed independently from an ingress point through a switching fabric to an egress point. Such network elements may route or switch traffic from both single-cell packet traffic flows and variable-size packet traffic flows. Upon reaching an egress card of the network element on a frame-based interface, the cells of a variable-size packet are reassembled into packets, queued and transmitted from the network element. Generally, traffic flows can contain packets of any size, where packets require a varying number of cells to represent them. Some traffic flows may not contain random packet sizes. One such flow, denoted a single-cell packet traffic flow, contains only packets that can be represented by one cell. A single-cell packet traffic flow is similarly reassembled into packets, queued and transmitted from the network element.
As network elements are required to route and switch data from an increasing number of traffic flows, a network element may reuse reassembly queues for more than one traffic flow to reduce the hardware resources required to service all of the traffic flows. If reassembly queues are not shared, a large number of reassembly queues are required, one to service each traffic flow. A reassembly queue must wait for all cells of a packet to be reassembled before queuing and transmitting the frame from the network element. If traffic flows containing relatively small packets and traffic flows with relatively larger packets share a reassembly queue, the smaller packets may be queued behind larger packets being reassembled into frames. This may cause delays to the traffic flow containing the small packets.
There is a need for a system and method for reassembling packets in a network element that reduces the resources required to reassemble packets and enable efficient processing of certain traffic flows.